令t = 2^x,dt = 2^x ln2 dx∫ 2^x/(1 + 2^x + 4^x) dx= ∫ t/(1 + t + t²) * 1/(t ln2) dt= 1/ln2 ∫ dt/[(t + 1/2)² + 3/4]令t + 1/2 = √(3/4) tanz,dt = √3/2 sec²z dz= 1/ln2 ∫ (√3/2 sec...